Heiko Carstens f5c8b96010 s390/uaccess: use sane length for __strncpy_from_user() ... The average string that is copied from user space to kernel space is rather short. E.g. booting a system involves about 50.000 strncpy_from_user() calls where the NULL terminated string has an average size of 27 bytes. By default our s390 specific strncpy_from_user() implementation however copies up to 4096 bytes, which is a waste of cpu cycles and cache lines. Therefore reduce the default length to L1_CACHE_BYTES (256 bytes), which also reduces the average execution time of strncpy_from_user() by 30-40%. Alternatively we could have switched to the generic strncpy_from_user() implementation, however it turned out that that variant would be slower than the now optimized s390 variant. Reported-by: Al Viro <viro@ZenIV.linux.org.uk> Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Reviewed-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>		2017-05-09 10:43:24 +02:00
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delay.c
find.c
Makefile
mem.S
probes.c
spinlock.c
string.c
uaccess.c	s390/uaccess: use sane length for __strncpy_from_user()	2017-05-09 10:43:24 +02:00
xor.c